Another example of genetic engineering in plant is the production of new varieties which emit a sky-blue glow when stressed. The amount of light emitted indicates the nature of the stress, such as drought, wind and exposure to frost. The bioluminescent protein aequorin occurs naturally in a species of blue jellyfish. Scientists have extracted the gene for this protein and have inserted it into some crop plant. The protein is sensitive to the level of calcium ions in plant cells, and stressed plant cells contain abnormally high levels of calcium ions. The protein undergoes a change to give the plant a coloured glow. Scientists hope that eventually these genetically engineered plant can be positioned among normal plant to act as living biosensors
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